On 9/24/2011 1:43 AM, DougC wrote:
On 9/23/2011 11:39 PM, Ignoramus14736 wrote:
I had a 17 year old diskette (1994) with some of my old C code
archives from 1988 or so. I could never get around to reading it,
finally bought a USB diskette reader. To my utter surprise, I could
read it and recovered all archives. Now I have my old MS-DOS library
that I wrote and made money using. Amazing...

You lucked out.
As I recall, 5.25's might hold for ~3 years.
3.5's might go for ~5 years; beyond that was iffy.

The hard drives were total opposites though--they could easily read &
write data 10-15+ years if they were retired before they had
mechanically failed.

I've had no problem reading 5.25 disks written in the early 80s, but I
have had problems with the disk drive being inop - I think their
longevity is much longer than you suggest - maybe that's a worst case.
Just as CDs were to have a 10 year max shelf life and the printed ones
(aluminized) seem to (so far) be fine at over 25 years